There is a known study project on quantum cryptographic communication, called SECOQC (secure communication based on quantum cryptography). The SECOQC proposes technologies of functions used to exchange keys based on random numbers generated through QKD (quantum key distribution) and then distributed and accumulated in a plurality of nodes, a protocol called Q3P (quantum point to point protocol), and the like.
The QKD is a method of realizing an enhancement in security of the next generation communication, and the security of a service thereof is important. For example, the QKD is a revolutionary technology capable of providing an absolute secure communication environment.
In the related art, however, if the security of a cryptographic key generated in a system using the QKD is not ensured, the absolute security of communication using the QKD may not be realized. In particular, a cryptographic key preserved inside may leak due to attacks from a network, such as attacks to a communication node and a service provided with the cryptographic key from a route through which the cryptographic key is distributed. That is, a countermeasure against so-called cyber-attacks is a task.